Hybrid inorganic-organic perovskites stand out as unique photovoltaic materials due to their exceptional optical and electronic properties. Here, we study in-plane carrier diffusion in perovskite thin films via time-resolved imaging of the photoluminescence from a diffraction-limited spot. Fitting to a 3D diffusion model allows extraction of both diffusion and recombination coefficients. Our results show two regimes of carrier diffusion, with a very rapid spreading large D = (0.968 ± 0.003) cm2s-1 observed at short times, within a measurement window of ~1 ns, and a much smaller D = (7 ± 1) × 10-3 cm2s-1 in a window of 200 ns. To investigate the rapid spreading at short times, we explicitly consider the effect of photon recycling within the plane of the film. We find that photon recycling has a negligible impact on such measurements, with the exception of a small increase in the intensity of the tails of the luminescence spot.
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